On Thu, Jul 30, 2015 at 01:29:01AM +0200, Rafael J. Wysocki wrote: > On Wednesday, July 29, 2015 03:37:43 PM Greg KH wrote: > > On Thu, Jul 30, 2015 at 01:01:21AM +0200, Rafael J. Wysocki wrote: > > > On Wednesday, July 29, 2015 02:19:16 PM Greg KH wrote: > > > > On Fri, Jun 26, 2015 at 02:32:47PM +0530, Viresh Kumar wrote: > > > > > ->add_dev() may fail and the error returned from it can be useful for > > > > > the caller. > > > > > > > > > > For example, if some of the resources aren't ready yet and > > > > > -EPROBE_DEFER > > > > > is returned from ->add_dev(), then the owner of 'struct > > > > > subsys_interface' may want to try probing again at a later point of > > > > > time. And that requires a proper return value from ->add_dev(). > > > > > > > > > > Also, if we hit an error while registering subsys_interface, then we > > > > > should stop proceeding further and rollback whatever has been done > > > > > until > > > > > then. Break part of subsys_interface_unregister() into another > > > > > routine, > > > > > which lets us call ->remove_dev() for all devices for which > > > > > ->add_dev() > > > > > is already called. > > > > > > > > > > Cc: 3.3+ <[email protected]> # 3.3+ > > > > > Fixes: ca22e56debc5 ("driver-core: implement 'sysdev' functionality > > > > > for regular devices and buses") > > > > > > > > I don't see how this is a stable bug fix, what is resolved by it that > > > > doesn't work today? Is there some code that is expecting this > > > > functionality that has never been present? > > > > > > > > I'll go queue it up, but I don't think it is -stable material, but feel > > > > free to change my mind. > > > > > > There is a small problem with it that I've already pointed out to Viresh. > > > > > > Namely, while changing subsys_interface_(un)register() to handle return > > > values from ->add_dev(), it doesn't do the same thing in > > > bus_probe_device() > > > which I believe it should for consistency at least. > > > > Oops, sorry, missed that response. I'll go drop this patch then, thanks > > for letting me know. > > > > > But then, the question is whether or not the probing should fail and > > > what if device_attach() returns 0 and one of the ->add_dev() callbacks > > > returns an error. > > > > That's a total mess... > > > > Given that there are almost no uses of this api, I think people should > > work it out before any more start to pop up :) > > cpufreq is one of the users and that's where the problem is, but in my opinion > it should be addressed in a different way. > > But while we are at it, should the ->add_dev and ->remove_dev callbacks in > struct subsys_interface return an int if their return values are always > ignored? Maybe it would be better to redefine them to be void to make it > clear > that they can't fail?
void makes sense to me. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
